drm/i915: Constify adjusted_mode

Make adjusted_mode const whereever we don't have to modify it. This only
covers cases when we have a local adjusted_mode variable, and doesn't
make any difference for cases where we just dereference
pipe_config->adjusted_mode.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 06a2b10..77f7330 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1587,7 +1587,7 @@
 	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
 	enum port port = dp_to_dig_port(intel_dp)->port;
 	struct intel_crtc *crtc = to_intel_crtc(encoder->base.crtc);
-	struct drm_display_mode *adjusted_mode = &crtc->config->base.adjusted_mode;
+	const struct drm_display_mode *adjusted_mode = &crtc->config->base.adjusted_mode;
 
 	intel_dp_set_link_params(intel_dp, crtc->config);